Olympic champion Aries Merritt will go for world 110m hurdles gold in Beijing on Friday just a few days before he undergoes a kidney transplant.

The brave bid by the world record-holder, who will receive a kidney from his sister on Tuesday, highlights day seven at the world championships along with a wide-open women's 200m.

Merritt ended 2012 with an Olympic gold medal and a world-record time of 12.80, but a year later was told he may never run again after being diagnosed with a rare kidney disease.

After struggling for most of 2013, Merritt's health deteriorated after the world championships in Moscow, his kidney function down to just 15 percent when he checked into hospital.

"I'm here for mental sanity more than anything," said the American.

"I don't want to be sitting in my house awaiting surgery. I'd rather be out living life to the fullest. Who knows, this could potentially be my last championship if surgery doesn't go well."

The 30-year-old Merritt clocked a season's best 13.08 seconds to win his semi-final in the quickest overall time.

Defending champion David Oliver will challenge but the race is lacking Orlando Ortega, the fastest man so far in 2015 who is ineligible after switching from Cuban to Spanish nationality.

The women's 200m final is missing 100m champion Shelly-Ann Fraser-Pryce, who opted out, leaving a possible opening for Dutch 100m silver-medallist Dafne Schippers.

+ Merritt in last race before kidney surgery

+ Women's 200m wide open without Fraser-Pryce
Source: AFP